Re: [patch] CFS scheduler, -v12

[Peter Williams <pwil3058@bigpond.net.au>]

Siddha, Suresh B wrote:
> On Thu, May 24, 2007 at 12:43:58AM -0700, Peter Williams wrote:
> > Peter Williams wrote:
> > > The relevant code, find_busiest_group() and find_busiest_queue(), has a 
> > > lot of code that is ifdefed by CONFIG_SCHED_MC and CONFIG_SCHED_SMT and, 
> > > as these macros were defined in the kernels I was testing with, I built 
> > > a kernel with these macros undefined and reran my tests.  The 
> > > problems/anomalies were not present in 10 consecutive tests on this new 
> > > kernel.  Even better on the few occasions that a 3/1 split did occur it 
> > > was quickly corrected to 2/2 and top was reporting approx 49% of CPU for 
> > > all spinners throughout each of the ten tests.
> > >
> > > So all that is required now is an analysis of the code inside the ifdefs 
> > > to see why it is causing a problem.
> >
> > Further testing indicates that CONFIG_SCHED_MC is not implicated and
> > it's CONFIG_SCHED_SMT that's causing the problem.  This rules out the
> > code in find_busiest_group() as it is common to both macros.
> >
> > I think this makes the scheduling domain parameter values the most
> > likely cause of the problem.  I'm not very familiar with this code so 
> > I've added those who've modified this code in the last year or 
> > so to the 
> > address of this e-mail.
>
> What platform is this? I remember you mentioned its a 2 cpu box. Is it
> dual core or dual package or one with HT?

It's a single CPU HT box i.e. 2 virtual CPUs.  "cat /proc/cpuinfo" produces:

processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 3
model name      : Intel(R) Pentium(R) 4 CPU 3.20GHz
stepping        : 4
cpu MHz         : 3201.145
cache size      : 1024 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 1
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge 
mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe 
constant_tsc pni monitor ds_cpl cid xtpr
bogomips        : 6403.97
clflush size    : 64

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 15
model           : 3
model name      : Intel(R) Pentium(R) 4 CPU 3.20GHz
stepping        : 4
cpu MHz         : 3201.145
cache size      : 1024 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 1
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge 
mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe 
constant_tsc pni monitor ds_cpl cid xtpr
bogomips        : 6400.92
clflush size    : 64


Peter
--
Peter Williams                                   pwil3058@bigpond.net.au

"Learning, n. The kind of ignorance distinguishing the studious."
 -- Ambrose Bierce
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